1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device, more particularly, a semiconductor device having a silicon carbide substrate and a method for manufacturing such a semiconductor device.
2. Description of the Background Art
Japanese Patent Laying-Open No. 2008-288349 (Patent Literature 1) discloses an n type IGBT (Insulated Gate Bipolar Transistor) employing a silicon substrate. Such an IGBT has a p type collector layer, which is formed by means of ion implantation and heat treatment after forming a structure of the emitter side on a silicon substrate.
In recent years, instead of a silicon substrate, use of a silicon carbide substrate has been considered as a substrate for a power semiconductor device. An impurity provided in silicon carbide (SiC) by means of ion implantation is activated normally at a heat treatment temperature of approximately 1500° C. or greater, which is much higher than the heat treatment temperature for activating an impurity provided in silicon by means of ion implantation. Accordingly, if the technique of Japanese Patent Laying-Open No. 2008-288349 is applied to a method for manufacturing an IGBT using a silicon carbide substrate, the structure of emitter side is damaged due to the high-temperature heating. Accordingly, it is difficult to apply this technique.
Japanese National Patent Publication No. 2010-529646 (Patent Literature 2) discloses that when manufacturing an IGBT using a silicon carbide substrate, a p type collector layer is formed on an n type silicon carbide substrate by means of epitaxial growth, then a structure of emitter side is formed, and then the n type silicon carbide substrate is removed.
According to the technique described in Japanese National Patent Publication No. 2010-529646, epitaxial growth of p type SiC is required to form the p type collector layer. However, this technique is highly difficult. In particular, it is highly difficult to attain the epitaxial growth of p type SiC on an n type silicon carbide substrate, which can be manufactured readily to have higher quality and larger size than a p type silicon carbide substrate.